Power converters, which convert DC power into AC power and/or AC power into DC power, include semiconductor modules each having integrated therein with semiconductor elements, such as insulated gate bipolar transistors (IGBTs). The power converters also include a smoothing capacitor electrically connected to the semiconductor modules. Japanese Patent Application Publication No. 2012-217322, which will be referred to as a published patent document, is an example of such power converters.
The power converter disclosed in the published patent document, which will be referred to as a conventional power converter, performs on-off switching operations of the semiconductor elements to thereby convert DC power supplied from a DC power source into AC power. The conventional power converter also smooths the DC power supplied to the semiconductor elements using the smoothing capacitor.
The semiconductor modules and the smoothing capacitor are electrically connected to each other with a pair of positive and negative busbars. The conventional power converter also includes a discharge resistor connected in parallel to the smoothing capacitor via the positive and negative busbars. The negative busbar is connected to a ground.
That is, the conventional power converter enables electrical charge stored in the smoothing capacitor to be discharged as a discharge current via the discharge resistor to the ground.
The discharge current flowing through the discharge resistor causes the temperature of the discharge resistor to increase, resulting in heat being generated from the discharge resistor. The heat generated from the discharge resistor is conducted to the smoothing capacitor via the pair of positive and negative busbars.
Because each of the positive and negative busbars is comprised of a metal plate, each of the positive and negative busbars has a relatively high heat capacity. Even if heat generated from the discharge resistor is conducted to the pair of positive and negative busbars, the high thermal capacitance of each of the positive and negative busbars causes less increase in the temperature of the positive and negative busbars, resulting in a smaller amount of heat being conducted from the positive and negative busbars to the smoothing capacitor. The conventional power converter therefore restricts an increase in the temperature of the smoothing capacitor.